Invariance Testing of the Disablement in the Physically Active Scale

Abstract

Context The increased emphasis on implementing evidence-based practice has reinforced the need to more accurately assess patient improvement. Psychometrically sound, patient-reported outcome (PRO) measures are essential for evaluating patient care. A PRO instrument that may be useful for clinicians is the Disablement in the Physically Active (DPA) scale. Before adopting this scale, however, researchers must evaluate its psychometric properties, particularly across subpopulations. Objective To evaluate the psychometric properties of the DPA scale in a large sample using confirmatory factor analysis procedures and assess structural invariance of the scale across sex, age, injury status, and athletic status groups. Design Observational study. Setting Twenty-two clinical sites. Participants Of 1445 physically active individuals recruited from multiple athletic training clinical sites, data from 1276 were included in the analysis. Respondents were either healthy or experiencing an acute, subacute, or persistent musculoskeletal injury. Main Outcome Measure(s) A confirmatory factor analysis was performed on the full sample, and multigroup invariance testing was conducted to assess differences across sex, age, injury status, and athletic status. Given the poor model fit, alternate model generation was used to identify a more parsimonious factor structure. Results The DPA scale did not meet contemporary fit index recommendations or the criteria to demonstrate structural invariance. We identified an 8-item model that met the model fit recommendations using alternate model generation. Conclusions The 16-item DPA scale did not meet the model fit recommendations and may not be the most parsimonious or reliable measure for assessing disablement and quality of life. Use of the 16-item DPA scale across subpopulations of interest is not recommended. More examination involving a true cross-validation sample should be completed on the 8-item DPA scale before this scale is adopted in research and practice.

Exploring the Psychometric Properties of the Disablement in the Physically Active Scale Short Form-8 in Adolescents

“…5,6 Although the scale has been recommended for use in practice and research, [5][6][7] a number of concerns regarding the psychometric properties of the scale have been raised recently. 8,9 Specifically, researchers noted high correlation values between hypothesized factors in the scale (eg, Impairment and Disability), suggesting multicollinearity and model misspecification. 8,9 Thus, researchers recommended that modifications to the DPA Scale be made and, subsequently, proposed a short form version of the scale (ie, the DPA SF-8).…”

“…8,9 Specifically, researchers noted high correlation values between hypothesized factors in the scale (eg, Impairment and Disability), suggesting multicollinearity and model misspecification. 8,9 Thus, researchers recommended that modifications to the DPA Scale be made and, subsequently, proposed a short form version of the scale (ie, the DPA SF-8). 8 The psychometric issues noted in the original DPA Scale (eg, multicollinearity) were not present in the DPA SF-8, and the short version had improved model fit while also reducing patient and clinician administrative burden due to the condensed subset of items.…”

“…8 The psychometric issues noted in the original DPA Scale (eg, multicollinearity) were not present in the DPA SF-8, and the short version had improved model fit while also reducing patient and clinician administrative burden due to the condensed subset of items. 8,9 The DPA SF-8 retains 8 of the original 16 items in the DPA Scale and consists of two factors: a physical summary factor (PHY factor; 4 items) and a quality-of-life factor (QOL factor; 4 items). Items in the PHY factor are related to a patient's perceived physical impairment and functional limitation, whereas items in the QOL factor are related to perceived quality of life.…”

“…Items in the PHY factor are related to a patient's perceived physical impairment and functional limitation, whereas items in the QOL factor are related to perceived quality of life. Preliminary results have demonstrated improved psychometrics, 8,9 but further testing is still needed prior to adoption into research and practice. In particular, psychometric analysis of the DPA SF-8 has not been performed using a sample of participants who only answered the 8 items; thus, the possible responses to the 8 items retained may have been influenced by the additional 8 items subsequently removed to create the DPA SF-8.…”

“…Furthermore, most participants utilized in the previous study were over the age of 18, and it is recommended to assess the scale psychometrics in an adolescent athlete population to ensure the items are appropriate for members of this demographic group. [8][9][10] Therefore, the purpose of this study was to conduct a confirmatory factor analysis (CFA) on the DPA SF-8 to determine model fit in an adolescent athlete population.…”